Abstract: The invention provides a device for reducing ingress noise in a digital signal, comprising a noise predictor for predicting an amount of ingress noise in the digital signal based on past samples of the ingress noise, and a subtractor for subtracting the predicted amount of ingress noise from the digital signal. Channel distortion is compensated for by a noise-independent equalizer, such as a ZF equalizer, placed upstream of the noise predictor. The device may be incorporated, for example, in a cable modem termination system (CMTS) of an hybrid fiber/coax (HFC) network.

Abstract: The invention provides a device for reducing ingress noise in a digital signal, comprising a noise predictor for predicting an amount of ingress noise in the digital signal based on past samples of the ingress noise, and a subtractor for subtracting the predicted amount of ingress noise from the digital signal. Channel distortion is compensated for by a noise-independent equalizer, such as a ZF equalizer, placed upstream of the noise predictor. The device may be incorporated, for example, in a cable modem termination system (CMTS) of an hybrid fiber/coax (HFC) network.

Abstract: An embodiment of a method for decoding a received signal function of at least a channel matrix H, and of a first and second symbols s1 and s2 belonging to a signal constellation. The method comprises the steps of: selecting a set of values of the first symbol s1 in the signal constellation; for each selected value of the first symbol s1: estimating the value of the second symbol s2 to generate an estimated value of the second symbol; calculating an Euclidean distance between the received signal and a noiseless signal defined by the first symbol with said selected value and by the second symbol with said estimated value; selecting the minimal Euclidean distance among the Euclidean distances respectively calculated for the different selected values of the set of possible values of the first symbol; and selecting decoded first and second symbols corresponding to the selected minimum Euclidean distance.

Abstract: A peak power reduction method for wireless communication systems is proposed in which a constellation shaping is applied on input data symbols in order to reduce the peak power of the signal samples to be transmitted by the communication system. According to the invention, the symbols are modified using functions each representing the contribution of a symbol to the output signal samples of large magnitude.

Abstract: The invention provides a device (D2) for reducing ingress noise in a digital signal, comprising a noise predictor (20) for predicting an amount of ingress noise in the digital signal (sn) based on past samples of the ingress noise, and a subtractor (21) for subtracting the predicted amount of ingress noise from the digital signal. Channel distortion is compensated for by a noise-independent equalizer (25), such as a ZF equalizer, placed upstream of the noise predictor (20). The device (D2) may be incorporated, for example, in a cable modem termination system (CMTS) of an hybrid fiber/coax (HFC) network.

Abstract: The invention provides a device (D2) for reducing ingress noise in a digital signal, comprising a noise predictor (20) for predicting an amount of ingress noise in the digital signal (sn) based on past samples of the ingress noise, and a subtractor (21) for subtracting the predicted amount of ingress noise from the digital signal. Channel distortion is compensated for by a noise-independent equalizer (25), such as a ZF equalizer, placed upstream of the noise predictor (20). The device (D2) may be incorporated, for example, in a cable modem termination system (CMTS) of an hybrid fiber/coax (HFC) network.

Abstract: In a transmission method in a multiple access radiocommunication system with orthogonal transmission resources, to cater for a number of users greater than the number of transmission resources of the system, at least one of the transmission resources is shared at a given time by at least two users. The users sharing a transmission resource change with time so as to divide the deterioration of the signal to noise ratio resulting from such sharing as evenly as possible between the various users. The deterioration of the signal to noise ratio is further reduced by differentiating the signals corresponding to users sharing the same resource at a given time in terms of their transmit level.

Abstract: The invention provides a device (D2) for reducing ingress noise in a digital signal, comprising a noise predictor (20) for predicting an amount of ingress noise in the digital signal (sn) based on past samples of the ingress noise, and a subtractor (21) for subtracting the predicted amount of ingress noise from the digital signal. Channel distortion is compensated for by a noise-independent equalizer (25), such as a ZF equalizer, placed upstream of the noise predictor (20). The device (D2) may be incorporated, for example, in a cable modem termination system (CMTS) of an hybrid fiber/coax (HFC) network.

Abstract: The invention provides a method of increasing by M, where M is any integer, the number N, where N is any integer greater than or equal to 2, of calls set up between a central unit and remote units of a code division multiple access network, N first group calls plus M second group calls being able to be set up simultaneously in this way and each using an internal spreading code and an external scrambling code. In accordance with the invention, first interference caused by first group calls in each second group call is synthesized and the first synthesized interference caused by first group calls is subtracted from each second group call. Similarly, a first interference caused by second group calls in each first group call is synthesized, and the first synthesized interference caused by second group calls is subtracted from each first group call.

Abstract: Using CDMA encoding and spectrum spreading with a factor N, more than N messages are transmitted although N is a theoretical limit for this type of encoding. Encoding uses orthogonal sequences for a first group of N messages and random or pseudo-random sequences PN for a second group of M-N additional messages. On reception, the N messages of the first group are decoded and detected. Their interference is subtracted from the second group of M-N messages before detecting the M-N messages. In a second iteration, the interference of the M-N messages using PN sequences is estimated and subtracted from the N first messages before a second detection on the first group of N messages. Detection is then repeated for the second group of M-N messages after subtracting the interference of the first group of N messages and the mutual interference of the M-N messages.

Abstract: A device for reducing the jitter caused by pointer adjustments in a digital telecommunication network comprising of a circuit inserting in the vicinity of each phase step caused by a pointer adjustment, a plurality of smoothing phase steps in accordance with a deterministic smoothing pattern in order to eliminate, after having passed through a conventional desynchronizer, the quantifying effects of the phase steps. Provision also is made, for the case in which each phase step caused by a pointer adjustment comprises a plurality of bits, in that a control circuit is present to resolve the step into a plurality of elementary steps and to control the insertion of these steps in a manner matched to the rate of occurrence of pointer adjustments. In particular, the device applies to networks based on Synchronous Digital Hierarchy.

Abstract: An adaptive predistortion circuit with memory for a digital transmission system includes a set (10) of input registers storing various consecutive data symbols a predistortion circuit (11) for predistorting the data of the consecutive data symbols before they pass through a modulator (14) and then through an amplifier (15) and an adaptation circuit (19) which, in response to a demodulation (16, 17.sub.1, 17.sub.2, 18.sub.1, 18.sub.2) of the stream of transmitted data symbols continuously adapts the predistortion circuit (11) to the stream of input data symbols. The adaptation circuit (19) includes a set (21) of counters/accumulators which determine the center of gravity of the smeared spots (clouds) created by the distortion by calculating a set of errors that is used for adapting the predistortion circuit (11). Preferably, the predistortion circuit is a random access memory.

Abstract: An adaptive predistortion circuit for a digital transmission system includes a predistortion circuit (52.sub.1, 52.sub.2, 52.sub.3) for predistorting the input data before they pass through a modulator (56) and then through an amplifier (57), and an adaptation circuit (61.sub.1, 61.sub.2, 61.sub.3) for continuously adapting the predistortion circuit to the stream of input data in response to a demodulation of the stream of transmitted data. The predistortion circuit further includes an encoder (51) which, on a first path, in response to digital data a.sub.k, generates digital data b.sub.k which leave a first predistortion circuit (52.sub.1) in a predistorted manner in-phase with the symbol clock, on a second path, digital data c.sub.k which leave a second distortion circuit (52.sub.2) in a predistorted manner phase-shifted by T/3 relative to the symbol clock and on a third path, digital data d.sub.k which leave a third predistortion circuit (52.sub.

Abstract: Predistortion arrangement (9) for a digital transmission system transmits complex input data of a constellation by means of a modulator (14) and a power amplifier (15) which distorts the data. The arrangement comprising a predistortion circuit (11) which predistorts the input data in opposite sense before they pass through the amplifier and a transmit filter (10) which applies oversampled filtered data encoded with 2N bits to the predistortion circuit (11) at the rate k/T. The predistortion circuit (11) first determines approximate values of the predistorted data on the basis of a portion of 2M bits of the field of 2N bits (M<N), which data are thereafter revised with the aid of the remaining portion of said field. The predistortion circuit includes for each channel a memory (112) addressed by the field of M bits which produces the approximate values of the predistorted data and an interpolation circuit (111) which derives therefrom the revised predistorted data.

Abstract: An adaptive predistortion circuit for a digital transmission system which comprises a predistortion circuit (52.sub.1, 52.sub.2) predistorting the input data prior to their entering a modulator (56) and thereafter an amplifier (57), and an adaptation circuit (61.sub.1, 61.sub.2) continuously adapting the predistortion circuit to the stream of transmitted data in response to a demodulation of the stream of transmitted data. The predistortion circuit further comprises an encoder (51) which, on the basis of digital data a.sub.k, generates on a first path digital data b.sub.k which leave a first predistortion circuit (52.sub.1) in a predistorted manner and in-phase with the symbol clock, and on a second path digital data c.sub.k which leave a second predistortion circuit (52.sub.2) in a predistorted manner and in phase-opposition to the symbol clock. The signals b.sub.k and c.sub.k are obtained by means of a polynomial encoding. The encoding may be effected with the aid of shift registers (62.sub.1 . . . 62.sub.

Abstract: A circuit for recovering the carrier of a digitally modulated wave comprising a voltage-controlled oscillator (17) that is controlled by an error signal .epsilon.(.phi.) in order to adjust the phase of the oscillator, the modulated wave being introduced into two channels, the one in phase (10) and the other in quadrature (20) with the carrier, the two channels being joined together by a phase comparator arrangement (25) which produces the error signal and a sampling clock (H1). The phase comparator arrangement (25) alternately operates as a phase detector and as a frequency detector and therefore comprises an apparatus for selecting received signal points with the aid of selection zones formed by ring segments, situated around certain states of the signal constellation.

Abstract: A circuit for recovering the carrier of a digitally modulated wave having a phase symmetry 2.pi./M, wherein M is the order of the symmetry, includes means for automatic and fast acquisition comprising a voltage-controlled oscillator having an output supplying said carrier and a control input to which an error signal .epsilon.(.phi.) is applied in order to change the oscillator phase and to adjust it to the phase of the digital modulated wave. This wave is introduced in two channels, one being in phase and the other being in quadrature with the carrier, each comprising the series arrangement of: a demodulator, a low-pass filter, reconstruction means for reconstructing a signal and for determining the error between the filtered and reconstructed signals, the quadrature channel comprising in addition a 90.degree. phase shifter, the two channels being joined together with the aid of a phase comparator arrangement which produces a comparison signal and a variable-rate sampling clock.

Abstract: A digital data receiving arrangement, which adapts itself to channel variations of a transmission system, comprises an adaptive receiver stage (11), having an adaptive equalizer and at least one sampler, and producing, at a certain rate, complex samples y.sub.k from the input signal x(t), a decision circuit (14) supplying detected complex samples a.sub.k and an adaptive timing recovery circuit (12) determining the optimal sampling instant by minimizing a quadratic function J which represents the difference between y.sub.k and a.sub.k. The adaptive timing recovery circuit comprises a device (121) for shaping a primary clock signal in accordance with a secondary clock signal, whose period is twice the period of the primary clock and whose consecutive ascending edges are spaced in time by T.sub.1 and T.sub.2, said secondary clock producing alternately two sampling instants .tau. and .tau.+.DELTA..tau.. By minimizing the function J, on the basis of the difference determined for two instants .tau..sub.k and .tau..

Abstract: A method of and an arrangement for determining the optimum position of the reference tap of a master adaptive equalizer which adapts itself to variations of the transmission characteristics of a transmission channel in a digital system for transmitting data which are in general complex, such adaptation being effected by modifying sets of coefficients of transversal filters which modify the transmitted symbols. Simultaneously with the operation of the master adaptive equalizer, and in consecutive analyzing periods, a selection is made in accordance with a selection algorithm of the optimum positions of the reference taps of transversal filters in a slave adaptive equalizer, the coefficients of which are adapted in accordance with an adaptation algorithm.

Abstract: An adaptive equalizer arrangement for digital transmission system comprises at the output of the transmission channel a first in-phase path and in parallel with this first path, a second quadrature path, both paths being of the non-recursive transversal filter type having n branches and (n-1) delay circuits between the inputs of these branches, each of these n branches comprising, arranged in series, a mixer, a low-pass filter, a multiplier, and having their outputs connected to an adder which is followed by a sampling circuit and thereafter by a comparator circuit to decide the symbols to be transmitted from the outputs of these paths. The arrangement also comprises a third control path which comprises two subtracting circuits to determine the differences between the signals before and after decision and a control circuit of a voltage-controlled oscillator, 2n phase shifters and 2n multipliers.